A Multibeam Antenna Array with Controllable Gain Allocation

Multibeam synthesis often relies on iterative optimization, whose computational cost and convergence time can increase substantially when the gains of different beams are unevenly distributed, making direct control of their relative gains difficult. To address this issue, a multibeam array synthesis and gain-allocation method based on the weighted maximum power transfer efficiency formulation is proposed. The method is developed for operation at 5.8 GHz using an 8 × 8 microstrip transmitting array and a 3 × 3 receiving-ports configuration to synthesize one broadside beam and eight off-axis beams distributed in the azimuth plane. Rx-port locations define the beam directions, and a diagonal weighting matrix sets their relative gains. Given the full-port scattering parameters, the complex array excitation comes from one eigenvalue problem. With equal weights, the nine-beam pattern is maintained for off-axis angles of 35°, 45°, and 55°, with peak gains of 13.3, 12.0, and 11.8 dBi, respectively. At an off-axis angle of 45°, varying the weighting matrix adjusts the gain difference between the central beam and the average gain of the eight off-axis beams from 0 dB to +5 dB or -5 dB, while keeping the beam directions unchanged. The proposed method is intuitive to formulate, accounts for mutual coupling through the full-port S-parameters, and allows gain allocation among multiple beams.